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New Member

4006 RSM question WS-X4232-L3

I am setting up a VLAN lab but I have a question on the 4006 RSM configuration options. Assuming that my RSM is in MOD 2, I understand that from the SUP II's point of view it sees 2/1 and 2/2 connected because he see's the 2 "internal" Gig channels connected and ready. Now, when you want to take advantage of Layer 3 switching I don't know whether to configure trunking or port-channeling. I have overviewed some of my colleges' scrips and I can't figure out what the advantage is between trunking the internal links or Port-channeling them? Can somebody help me out.

6 REPLIES
New Member

Re: 4006 RSM question WS-X4232-L3

New Member

Re: 4006 RSM question WS-X4232-L3

From the L3 config sheet:

"Configuring the two gigabit connections between the switch and the router as two port Gigabit Ether Channel is just an option (probably the most efficient), but it is not mandatory. You can configure them as independent trunks or as access ports. It just needs to remain consistent with the configuration of the gigabit ports on the switch side."

First, you have to Trunk regardless of port channeling or not. This is how vlan info is passed between layer 2 ports. We've also performed the L3 RSM test install and configured the g2,g3 & 2/1,2/2 as port channels. Our thinking was that with Etherchannel there would be more available bandwidth, but not the case according to the document. It would be simpler to setup the port channel as apposed to independant trunked links because you will have to configure a trunk on each interface.

New Member

Re: 4006 RSM question WS-X4232-L3

The information you quoted from the document is accurate.

Now to answer your question, you don't have to trunk as you setting the vlan on the switchport (3/1 and 3/2) and hence you don't have to trunk. Obviously you can only set ports to one vlan each and hence you can route between only two vlans. So trunking is needed for more than 2 vlan routing. :)

Yes,Etherchannel would allow bundling of the Gigabit ports. Document never contradicts this fact.

If you configure as independent trunks then one of the port would be blocking if they are trunking the same vlans. But obviously one can trunk different vlans on each port in which case both would be forwarding for different vlans. Obviously as the document says and as you also feel, it is efficient to do trunking and channeling ;)

New Member

Re: 4006 RSM question WS-X4232-L3

Thanks for all the feedback guys but I have a more command specific question. In the following example..

What command would I need to type into the interface Port-Channel 1 to make sure it is in the native VLAN 1 ? Also, How do I verify that my RSM is also in the native VLAN as the SupII engine? Am I on the right track or am I totally confused? I would appreciate any more advice.

Current configuration:

!

version 12.0

no service pad

service timestamps debug uptime

service timestamps log uptime

no service password-encryption

!

hostname RSM-ADMIN-1

!

enable password cisco

!

ip subnet-zero

no ip domain-lookup

!

!

!

interface Port-channel1

no ip address

no ip directed-broadcast

hold-queue 300 in

!

interface Port-channel1.48

encapsulation dot1Q 48

ip address 172.20.48.1 255.255.255.0

ip helper-address 172.20.48.254

no ip directed-broadcast

!

Thanks,

~zo

New Member

Re: 4006 RSM question WS-X4232-L3

I don't think it is a good idea to use port channel, for it does not support ACL.

On the switch engine, the command 'show trunk' will show you the native vlan.

On the RSM, you specify the native vlan with command 'encapsulation dotq 1 native'.

New Member

Re: 4006 RSM question WS-X4232-L3

Alonzo,

FYI:

We are going to have to break the portchannel because we need to place an access list on those interfaces. You can't apply an access list to a portchannel sub-interface.

R.

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